So, im still a recruit and i havent yet picked my MOS, mostly because im not qualified for the jobs i am interested in, because of my criminal record.  But i was wondering how difficult it is and how you would go about changing jobs after being in for a couple years.  My recruiter told me after being in for a couple years, and "proving myself" i would be able to get the security clearance i need.

First you need to understand, when it comes to changing your mos, it isnt as though you can simply walk into an your commander's office one day and simply "apply" for a new job. There are two primary ways your mos can change. One, when your window for re-enlistment opens up (usually midway through your initial contract), you can choose to change your mos to something other than what you signed up for, and perhaps by that time, you could have "proven yourself" enough to get the mos you really want. Second, if your mos were to ever become phased out and you are placed in a new MOS by way of hands-on training in this new job; that is, training you would receive at your duty station, rather than a return trip to an AIT school for that job. Also, depending on what exactly your criminal record entails, and how you handle that aspect of it through the courts, would determine whether or not you get that much needed security clearance. Showing that you are a nice guy, or that you are intelligent enough to perform the MOS you really want to do, will not sway the minds of the decision makers in regards to your clearance status.